Fix OpaqueClosure show method

This file moved into Base.Experimental late in the PR cycle, which
doesn't have Base.show imported. Just move the show methods to
show.jl, since OpaqueClosure is defined in Core anyway - might as
well.

Author: Keno

base/opaque_closure.jl

@@ -1,14 +1,3 @@
-function show(io::IO, oc::Core.OpaqueClosure)
-    A, R = typeof(oc).parameters
-    show_tuple_as_call(io, Symbol(""), A; hasfirst=false)
-    print(io, "::", R)
-    print(io, "->◌")
-end
-
-function show(io::IO, ::MIME"text/plain", oc::Core.OpaqueClosure{A, R}) where {A, R}
-    show(io, oc)
-end
-
 """
     @opaque (args...) -> body
 

base/show.jl

@@ -2848,3 +2848,15 @@ end
 bitshow(B::BitArray) = bitshow(stdout, B)
 
 bitstring(B::BitArray) = sprint(bitshow, B)
+
+# printing OpaqueClosure
+function show(io::IO, oc::Core.OpaqueClosure)
+    A, R = typeof(oc).parameters
+    show_tuple_as_call(io, Symbol(""), A; hasfirst=false)
+    print(io, "::", R)
+    print(io, "->◌")
+end
+
+function show(io::IO, ::MIME"text/plain", oc::Core.OpaqueClosure{A, R}) where {A, R}
+    show(io, oc)
+end

test/opaque_closure.jl

@@ -150,3 +150,6 @@ end
 mk_va_opaque() = @opaque (x...)->x
 @test mk_va_opaque()(1) == (1,)
 @test mk_va_opaque()(1,2) == (1,2)
+
+# OpaqueClosure show method
+@test repr(@opaque x->1) == "(::Any)::Any->◌"